Turanose is an isomer of sucrose comprising a glucose unit and a fructose unit linked via an α(1→3) bond. It is a typical sugar of honey, in which it is present in a low amount, generally between 0 and 3%.
It can, for example, be produced by partial hydrolysis of melezitose, thus producing an equimolar mixture of glucose and turanose (CS240545). In addition, it can also be produced through the action of a cyclomaltodextrin glucanotransferase of Bacillus stearothermophilus on a mixture of starch and fructose (JP5252974/93; Shibuya et al., 2004, J. Appl. Glycosci., 51, 223-227). The yield is only 45% and the method comprises two enzymatic steps.
Finally, it has been proposed to use a recombinant amylosucrase derived from Neisseria polysaccharea (NpAS) to convert sucrose to turanose (Wang et al., 2012, Food Chemistry, 132, 773-779). The yield is 56% and the method requires a recombinant enzyme.
It is known to those skilled in the art that turanose:                has a relatively weak sweetening power of 0.5 (the value 1 being assigned to sucrose) and a low cariogenicity,        can be readily crystallized, and        is highly soluble.        
In addition, turanose is an inhibitor of α-glucosidase, useful in the diagnosis of Pomp's disease.
It is also of interest in the food, cosmetic, pharmaceutical and diagnostic fields.
Turanose is also a message molecule. With other monosaccharides, turanose has thus been used to mimic the various sucrose signaling pathways in photosynthesis.
Turanose may also be involved in plant defense mechanisms, with the production of defensive substances via activation of MAPKs (Mitogen-Activated Protein Kinases).
Thus, alternative methods for producing turanose are useful and desired, in particular methods which are competitive at the industrial level.